This isnt a very good example of what you want. This was assuming the only content on the page was checkboxes.
Private Sub Command1_Click()
With browser.Document
'do some sort of loop through the checkboxes
browser.SetFocus
SendKeys "{TAB}"
SendKeys "{ }"
End With
End Sub
If you have the name of the form on the page, you can use something like.
browser.document.formname.checkbox.value = "1"
I think...